De-ASTContext-ify DeclContext.

Remove ASTContext parameter from DeclContext's methods. This change cascaded down to other Decl's methods and changes to call sites started "escalating".
Timings using pre-tokenized "cocoa.h" showed only a ~1% increase in time run between and after this commit.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@74506 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/ResolveLocation.cpp b/lib/Frontend/ResolveLocation.cpp
index 3908e89..d7a9b48 100644
--- a/lib/Frontend/ResolveLocation.cpp
+++ b/lib/Frontend/ResolveLocation.cpp
@@ -163,7 +163,7 @@
 void DeclLocResolver::VisitDeclContext(DeclContext *DC) {
   DeclLocResolver DLR(Ctx, Loc);
   for (DeclContext::decl_iterator
-         I = DC->decls_begin(Ctx), E = DC->decls_end(Ctx); I != E; ++I) {
+         I = DC->decls_begin(), E = DC->decls_end(); I != E; ++I) {
     DLR.Visit(*I);
     if (DLR.Finished()) {
       if (DLR.FoundIt())